In article <mailman.96.1151932460.20007.neur-sci at net.bio.net>,
polly jo <jopower at yahoo.com> wrote:
> I was wondering if the experts here would comment of
> the neuronal maturation and growth of dendrites ....
> the cellular processes involved, and the general time
> frame (I am just about aware that there are
> developmental time windows, and molecular cues
> ofcourse, however, i am not sure about the specific
> numbers that mature , that remain, that grow or stay
> during ones life time)
I'm not an expert, but I can tell you that there have been a lot of
studies of the maturation of dendrites (outgrowth, addition of spines,
pruning, etc.) during normal development. However it seems these
dendrites are able to be changed a lot even in the mature brain - the
guys at Karel Svoboda's lab have imaged dendrites and spines changing
shape from day-to-day in the adult mouse brain (last thing I looked at
was Trachtenburg et al 2002 I think). Tailby et al 2005 show that in the
barrel cortex of rats, which handles whisker inputs, cells will re-grow
and re-orient their dendrites on a huge scale in response to short-term
changes in whisker activity. However barrel cortex may be unusually
"plastic" in this respect.
So for growth, obviously guided protein synthesis, controlled by the
environment the dendrite is in (chemical signalling) and interactions
with other neurons and glia (very important), are the key players. For
time scale, a few hours (for a spine to grow or retract); a few days -
weeks for whole dendrites to be dismantled or rebuilt; or an entire
lifetime (the patterns built into yours and my brains as a result of all
our experience).
Cheers, MK.